The present invention relates to a continuous-rod cigarette manufacturing machine and, more particularly, to the means for forming the so-called continuous cigarette rod.
Cigarette manufacturing machines of the abovementioned type are already known, on which an essentially vertical duct is fed at the bottom from a continuous flow of tobacco particles and is closed off at the top by the bottom branch of a suction conveyor belt, looped round end rollers.
On the suction conveyor belt, a stream of shredded tobacco is formed which, at a point outside the vertical duct, known as the loading station, is dropped on to a strip of cigarette paper adhering to the top branch of a loop conveyor belt running over an essentially horizontal shelf. The conveyor belt forces the paper strip to wrap gradually round the stream of tobacco so as to form a continuous cylinder, the so-called continuous cigarette rod, which, as it comes off the shelf, is cut into single cigarettes by means of a rotary cutter.
Still according to known technology, as it moves between the duct and loading station, the tobacco stream is subjected to the action of a so-called shaving device consisting of a pair of tangent discs with cutting edges shaped so as to form the tobacco stream into two different thicknesses alternating at regular intervals. Once the paper strip has been wrapped round the stream of tobacco, the thicker stream sections are converted into more tightly-packed rod sections. The said rotary cutter is set, in relation to the shaving device, so as to cut the continuous rod at the mid point of the said tightly-packed section.
The purpose behind this is to provide single cigarettes with compact ends, capable of withstanding subsequent manufacturing stages (filter assembly and packing) with no noticeable loss of tobacco.
On known types of manufacturing machines, however, as the stream of tobacco is being transferred from the suction conveyor to the cigarette paper strip at the loading station, it tends to even out in thickness or, at best, the said thicker sections fall out of step in relation to the rotary cutter.
The reason underlying this drawback can be found in the withholding action exerted by a fixed element, known as a pressure element, over the rod forming shelf. The function of the said element is to control the tobacco stream, as it is dropped off the suction conveyor, and to guide and compact it, once it is deposited on the paper strip, so as to enable subsequent formation of the continuous cigarette rod.
Consequently, to prevent the rod from being cut outside the more tightly-packed sections, and consequent production of extremely poorly-packed cigarettes, the contour on the shaving discs is shaped so as to oversize the said tightly-packed sections.
Obviously, however, such a corrective measure also results in a considerable increase in the amount of tobacco required for manufacturing the cigarettes.